Packet switched networks are generally based on shared bandwidth topology. In this topology, each node has unlimited and uncontrolled access to network resources. A commonly used network access system, known as statistical multiplexing, transmits data simultaneously from any number of input devices attached to the network, and offers maximum utilization of the network's available bandwidth by assigning to each device unrestricted access to the network. However, with this kind of multiplexing, several inherent problems arise:                Network behavior is erratic and unpredictable due, in part, to collisions between data packets that different nodes are attempting to transmit at the same time.        Network resources are unfairly distributed, with ingress nodes which are closer to certain egress nodes getting much more bandwidth than ingress nodes which are remote from those egress nodes.        Traffic parameters, such as delay (the time lag between the departure of a signal from the source and the arrival of the signal at the destination) and jitter (the variance from the average delay), cannot be assured.        It is impossible to guarantee quality of service, in terms of assured bandwidth, bound delay and jitter, and packet loss, to differentiated customers or services, as defined in Service Level Agreements (SLAs).        
Conventional solutions and practices for data networks involve adding complex management protocols, which generally are based on packet-by-packet traffic handling and heavy error correction and data integrity algorithms. These solutions, however, are based on local (per hop) calculations and information, and are prone to errors due to global dynamic changes, e.g., a sudden rise in network resource use in one node that causes the network to be congested for the time (typically, a few seconds) it takes for the resource management protocols to stabilize the network. With conventional dynamic networks, only over-engineering of the network can assure that the peak network use is adequately met without disturbing guaranteed traffic. This results in under-utilization of network resources at other times.
One example of admission control of traffic based on per hop statistics is shown in US patent application 2004/0128384 to Rolia, et al. This application relates to admission control of applications in resource utility environments. The method of admission control includes determining the application's statistical demand profile for resources required by the application seeking admission; determining an assurance level of the resource utility; and admitting the application based on the statistical demand profile of the application, the assurance level of the resource utility, and statistical demand profiles of one or more applications currently hosted by the resource utility. This method has the following limitations:                1. The Rolia method utilizes no prior knowledge or rules of the applications resource usage, but only a computed statistical demand profile.        2. This method can only respond to learned resource demand and decide whether it can support it or not, without the ability to rate limit the demand, e.g., bandwidth demand, continuously and dynamically according to a predefined SLA.        3. The Rolia method cannot control resource consumption once an application is allowed to run. Rather, its only choice is whether or not to permit the application to run.        
Another example of a prior art solution is disclosed in U.S. Pat. No. 6,771,598 to Andrews. This patent describes a method for determining the admissibility of an offered session of traffic of a specified class to a server in a packetized communication network. The method involves defining an operating point for the server which represents the number of sessions of each respective class currently offered or currently being served, and determining whether this defined operating point falls within an admissible region. The admissible region consists of operating points for which the probability of violating a delay bound for any packet is below a threshold value. This method performs admission control based on calculation of each server's abilities based on some a priori knowledge of its behavior, and not based on actual traffic behavior throughout the network.
A further example is shown in U.S. Pat. No. 6,791,941 to Dziong, et al. This patent relates to tuning for connection admission control (CAC) algorithms in broadband ATM networks, which is accomplished using an overbooking technique based on aggregate effective bandwidth as an approximation to required bandwidth for given levels and classes of network traffic. Overbooking is introduced in small increments until a threshold value (such as a cell loss threshold value) is reached, at which point overbooking is reduced in a large step. Thus, this patent is based on a trial-and-error method for determining optimized rate control of each local traffic stream.
None of these prior art methods provides admission for data packets which is close to optimal. Accordingly, there is a long felt need for an access control mechanism which permits access to network resources based on global information, and it would be very desirable to have such a mechanism which provides more balanced utilization of network resources.